The present invention relates to a process for obtaining a vanadium-containing steel alloy for use in, e.g., steel making procedures.
More particularly, the vanadium-containing steel alloy is obtained using an iron based spent hydroconversion catalyst as the source of vanadium for the vanadium-containing steel alloy.
A significant aspect of the steel making industry is the addition of various chemical elements to the molten metal bath in order to obtain improved mechanical properties, corrosion resistance, and reactivity, as well as various other desired properties of the resulting alloyed steel.
These various chemical elements are normally added to the molten steel as an iron alloy because the melting point of the iron alloy is lower than the melting point of the pure metal.
One of the frequently used elements in steel production is vanadium. Vanadium is normally incorporated into steel as a strengthening agent by adding the vanadium to the molten bath of steel in the form of ferrovanadium.
A common procedure for obtaining ferrovanadium comprises the steps of reducing vanadium oxide with aluminum or silicon in the presence of iron in an electric furnace. Such a procedure may, more specifically, include the reduction of vanadium pentoxide fines with iron scraps or oxides and aluminum powder which are mixed together with a basic oxide such as calcium oxide and heated to ignition.
U.S. Pat. No. 4,165,234 to Kostyanoi et al. discloses a process for producing ferrovanadium alloys. Kostyanoi teaches the process of starting with a ferrovanadium slag; melting the slag; reducing the slag with a ferrosilicium and aluminum composition; removing slag from the reduced mixture; purging the remaining melt with oxygen to obtain a composition in the melt of 35% vanadium pentoxide as slag; discharging the remaining metal melt; and reducing the 35% vanadium pentoxide to obtain ferrovanadium.
DD-256685-A discloses an extraction wherein an iron-containing vanadium salt solution is processed by spent catalyst leaching to yield starting material (pure vanadium) for ferrovanadium production.
Various other processes for obtaining vanadium-containing steel have been disclosed offering advantages such as increased degree of assimilation of vanadium, increased quality of the metal, reduction in time required for the procedures, economical starting materials, enhanced open-hearth furnace productivity, and starting materials with high purity and low residual elements.
For example, U.S. Pat. No. 4,526,613 discloses a procedure for producing vanadium-containing alloys wherein the starting material is a pure vanadium trioxide which results in fewer impurities being imparted to the end product. Other procedures such as those listed above are disclosed in the following patents: SU 1194905-A, SU 1235968-A, SU 1407961 and SU 1097682.
Of the above, important advantages can be obtained through providing economically obtained starting materials. Accordingly, the process of the present invention discloses the use, as a starting material, of a spent iron based catalyst which has been used, for example, in a hydroconversion process for heavy hydrocarbon feedstocks. These spent catalysts typically have, as a result of the hydroconversion, large percentages of vanadium, as well as, less desirably, significant amounts of sulfur and coke.
Accordingly, a principal object of the present invention is to provide a vanadium-containing agglomerate which can be used in making steel alloys.
It is a further object of the present invention to provide a process for manufacturing such an agglomerate from a spent hydroconversion catalyst.
It is still another object of the present invention to provide a procedure whereby the so obtained agglomerate can be processed to obtain a vanadium-containing steel alloy.
It is a further object of the present invention to provide a useful application for the aforesaid spent catalyst which avoids economically and environmentally expensive disposal alternatives.
Further objects and advantages of the present invention will appear hereinbelow.